Currently, much of industrial and commercial cooling in a heat exchange is conducted by the use of evaporative cooling. Water in a re-circulating system absorbs heat from somewhere in a facility, building or a process (manufacturing, data processing, environmental control, and so forth), and then expels that latent heat, as to the atmosphere. Oftentimes in larger facilities like manufacturing or office buildings, this is by means of the coolant, typically water, being sprayed or spread in thin films while exposed to air moved by fans. This allows the water both to contact the cooler air and to transfer or release some of its heat energy by means of evaporation.
When water is evaporated as part of a cooling process, it leaves in the remaining water, or reservoir, its own dissolved minerals, albeit in much small concentrations. As fresh water is added to the system to make-up for the lost evaporated water, it too has its dissolved minerals. Thus, the overall level of dissolved mineral ions increases as heat is dissipated from the system in the form of lost moisture through evaporation.
Among the dissolved solids are so-called hard minerals like calcium and magnesium, which at certain concentrations precipitate out to form lime scale. In order to prevent these increased concentrations, total dissolved solids are typically monitored by means of the conductivity of the water. High dissolved solids water is removed, such as bled off through an automatic valve. Fresh water which is added to the system to make-up for the drained water then serves to dilute the dissolved solids in the overall system, and lowers the dissolved solids levels.
In theory, a water softener can replace the troublesome build-up of calcium and magnesium ions with sodium ions. Sodium ions do not harmfully precipitate. The art of cation resin water softening is well established and in wide use. The replacement of calcium and magnesium ions with sodium ions via water softening considerably raises the level of dissolved solids allowable in an evaporative cooling system. This, in turn, reduces the need for draining off system water and replacing it with fresher water, but replacement still must occur over time.
In general the industrial world is facing a scarcity of fresh water resources and consumers of water, private and commercial, are experiencing considerable increases in water costs. Evaporative cooling uses a large portion of the water consumed in commerce, institutions, and industry. In order to realize water conservation objectives, evaporative cooling systems operators are looking to raise the total dissolved solids levels in their re-circulating cooling water.
While treating the reservoir water in a “softening” process is possible, there are distinct draw backs. First, the water softener mechanism requires regular replenishment of solid salt. Second, water softeners are prone to some degree of mechanical failure, and significant intervention or service is occasionally required. Should the water softener have a problem producing soft water, either because of mechanical failure or failure to replenish the solid salt, the evaporative cooling system will experience an increase in hardness mineral concentration.
If the softener fails and the total dissolved solids setting is not lowered to concentrations below the threshold where lime scale precipitates, then substantial fouling will ensue. Thus, the need exists to monitor water softener performance and to automatically reset the evaporative cooling tower dissolved solids settings if it is likely that hardness minerals are entering the evaporative cooling system water.
A number of patents have addressed the use of water softeners for evaporative cooling, and some use a sensor array to determine water conditions and subsequently send water the system water through a softening bed. Such are U.S. Pat. No. 4,931,187, U.S. Pat. No. 7,595,000, and U.S. Pat. No. 6,746,609. None test the softener for it performance.
Some patents use conductivity sensors to monitor softener conditions, but none (as far as the Applicant herein understands), detect brine water in the drain line. None are integrated with evaporative cooling tower water chemistry. Such are U.S. Pat. No. 4,320,010, U.S. Pat. No. 7,556,738 and U.S. Pat. No. 7,329,338.